1. Field of the Invention
The present invention relates to a remote copy processing method, a program, and a system for establishing and executing a session in which a volume of a RAID device connected to a host serves as a copy source and a volume of another RAID device connected thereto by an inter-chassis path serves as a copy destination; and particularly relates to a remote copy processing method, a program, and a system for establishing and executing again the same session, according to instructions from the host, when the path is connected after the session is suspended due to blockage of the inter-chassis path during copying.
2. Description of the Related Arts
Conventionally, in remote copy performed between two RAID devices installed in separate chassis which are away from each other with a distance there between, as shown in FIG. 20, RAID devices 200 and 202 are connected to hosts 204 and 206, respectively, and, for example, according to a copy-instruction start command and session information issued from the host 204, a copy session is established between the RAID devices 200 and 202, thereby executing remote copy.
In this remote copy performed by establishing a session, the entire or partial data of a primary volume 208 of the first RAID device 200 which is specified as a copy source is transferred and copied to the same track position of a secondary volume 210 of the second RAID device 202 which is specified as a copy destination via an inter-chassis path 212.
If blockage occurs, while such remote copy is being executed, in the inter-chassis path 212 connecting the RAID devices 200 and 202, the session is forcibly released by a stop command from the host 204. In this case, although the session information can be deleted in the RAID device 200 of the copy source by releasing the session, the session information of the cancelled session remains in the RAID device 202 of the copy destination.
Then, when the chassis path 212 is connected, a start command and session information of the forcibly released session are issued from the host 202 so as to start over the remote copy from the beginning. However, the session information of the forcibly released session is remaining in the RAID device 202 of the copy destination; therefore, the start command and the session information received for establishing the same session again via the RAID device 200 result in a command error, and the session cannot be resumed. In such case, when the remaining session information is deleted by an instruction from the host 206 which is connected to the RAID device 202 of the copy destination, the forcibly cancelled session can be established thereafter by an instruction from the host 204, thereby starting over the remote copy from the beginning. [Patent Document] Japanese Patent Application Laid-Open (kokai) No. 2002-297455
Meanwhile, in an online backup system and the like, as shown in FIG. 2, the RAID device 202 for backup having no host is connected to the business-use RAID device 200 which is connected to the host 204 by the inter-chassis path 212, and, according to a copy-instruction start command and session information issued from the host 204, a copy session is established between the RAID devices 200 and 202, thereby executing remote copy, so as to generate a volume for backup in the RAID device 202. However, there is a problem that, in a case in which the RAID device 202 of the copy destination is not connected to any host, when blockage occurs in the inter-chassis path 212 and the session is forcibly released, the session information remaining in the RAID device 202 of the copy destination to which no host is connected cannot be deleted. In this case, the remaining session information is deleted by operations performed from a personal computer 214 for maintenance provided at the RAID device 202 of the copy destination, which takes labor and time since man-made operations are required. Particularly, if the copy destination is placed in, for example, a backup center at a remote place away from the copy source, a person in charge has to go to the copy destination from the copy source so as to perform operations of deleting the session information remaining in the copy destination. Therefore, there is a problem that start over of the forcibly released session of remote copy takes labor and time. According to the present invention is to provide a remote copy processing method, a program, and a system which enable quick start over of forcibly released remote copy by efficiently deleting the session information remaining in the copy destination having no host by instructions from a host connected to the copy source.